1. Field of the Invention
The present invention relates to a solid oxide fuel cell (hereinafter referred to as an SOFC) for generating electric energy through an electrochemical reaction and also to a method for manufacturing the same.
2. Description of the Prior Art
The following SOFCs are known: a high voltage output type tubular SOFC made by forming a plurality of single cells each comprising a fuel electrode, an electrolyte, an air electrode, and with an interconnection connecting the single cells in series each other on a porous support tube (Japanese Patent Laid-Open No. 73246/1979); a high current output type tubular SOFC made by forming a single cell comprising an inner electrode, an outer electrode, an electrolyte between the electrodes, and with an interconnection formed in a selected section of the inner electrode passing through the electrolyte and the outer electrode on a porous support tube. Each adjacent cell tubes are connected in series as the interconnection of a cell connecting to an outer electrode of an adjacent cell through a metallic felt and/or in parallel as the outer electrodes of adjacent cells connecting each other through a metallic felt (Japanese Patent Laid-Open No. 130381/1982); and a monolithic SOFC made by sandwiching a flat cell section comprising three layers, namely, a fuel electrode, an electrolyte, and an air electrode, between corrugated mutual-connection walls comprising three layers, namely, an air electrode, an interconnection, and a fuel electrode (Japanese Patent Laid-Open No. 100376/1985).
These prior SOFCs, however, have some problems in practical use like the output per volume of the tubular SOFC is not high because the porous support tube cannot be extremely thinned in view of its structure though the tubular SOFC can be comparatively easily manufactured, or the manufacture on the monolithic SOFC, such as cell fabrication, gas-sealing, and assembling, is very difficult though the monolithic SOFC has a good performance of a high output per volume.
In order to solve the above problems, the applicants of the present invention proposed an SOFC whose power generation efficiency is improved by decreasing the necessary strength of a support (porous part or inner electrode) and which can be easily assembled and its manufacturing method in Japanese Patent Application No. 106610/1990.
That is, the SOFC in the previous application is fabricated by arranging inner electrodes in a hollow section in the surface of a substrate using or without using a porous base provided on the surface of the substrate, forming an electrolyte and an outer electrode in order through means such as vapor deposition to form each of single cell sections and connecting them in series and in parallel by interconnections.
However, conventional manufacturing methods have a problem that, if a failure occurs in one cell section under fabricating cells, the whole assembly of cell stacks or cell sections may become defective because a plurality of cell sections are simultaneously manufactured or integrated on the substrate.
Moreover, there is a problem that the base is affected by heat when the film of each element of a cell section is formed because the cell section is formed on the substrate.